While NATO was initially just complaining the S-400 was incompatible with their own systems, top NATO General Petr Pavel told reporters this week that Turkey is likely to be punished by the alliance for not buying American.

“The principal of sovereignty obviously exists in acquisition of defense equipment, but the same way that nations are sovereign in making their decision, they are also sovereign in facing the consequences of that decision,” Pavel insisted.

“When it comes to democratic deficits, show me one single nation that is perfect. No one is perfect,” Pavel said.

“No one challenges the role of Turkey as an important ally at the very difficult crossroads of challenges to the alliance.”

Apparently the same leeway does not apply for the question of buying American weapons.

The missile deal with Russia “is a clear sign that Turkey is disappointed in the U.S. and Europe,” said Konstantin Makienko, an analyst at the Center for Analysis of Strategies and Technologies, a Moscow think-tank.

“But until the advance is paid and the assembly begins, we can’t be sure of anything.”

Russia’s S-400, and its predecessor the S-300, have been praised as advanced, cost-effective alternatives to American anti-aircraft systems.

The US is used to having a virtual monopoly on this market, by ensuring that no one buys Russian without facing some very public criticism.